Selecting only pencil lines in scanned drawing?

Hi fellas. I'm new to the forum and somewhat new to gimp.
I'm trying to select the pencil lines only from a scanned drawing and lose the white back ground so I can set the drawing only onto other layers. How would I go about doing this?

A common way of 'losing' a white background is with gimp menu Colors -> Color to Alpha
The default colour is white so you have nothing to do there, the alpha is transparency so you can put the result over another image.

Once you have removed the background, save the image as an .xcf file, this preserves the transparency for later editing.

Guessing you have something like this.
The chequer board denotes transparency.

Put a layer under as required. Save as an xcf file to preserve transparency and layers until you are finished.
Export as a png saves transparency but flattens the layers. Export as jpg loses transparency and flattens the layers.